While the traditional model of paleontology, the phylogenetic model, posits that features evolved slowly without any direct association with speciation, the relatively newer and more controversial idea of punctuated equilibrium claims that major evolutionary changes don't happen over a gradual period but in localized, rare, rapid events of branching speciation.
In 1983, Malmgren and colleagues published a paper called "Evidence for punctuated gradualism in the late Neogene Globorotalia tumida lineage of planktonic foraminifera.
"[1] This paper studied the lineage of planktonic foraminifera, specifically the evolutionary transition from G. plesiotumida to G. tumida across the Miocene/Pliocene boundary.
[1] Based on these findings, Malmgren and colleagues introduced a new mode of evolution and proposed to call it "punctuated gradualism.
[2] This study presents evidence of a species exhibiting punctuated and gradual evolution, while also having periods of relative stasis.
[5] Another related study focuses on the extent of undefined area when trying to compare the two modes of evolution making it difficult to isolate one model.
These factors along with replication time can create barriers when working to prove a single mode of evolution as being accurate.
The species that doesn't use the characteristic might begin to use it for an alternate function, causing difficulty when trying to track evolution.
This study challenges old conclusions and supports both models using more modern techniques providing current evidence for interpretation.